Re: [PATCH v3 4/4] net/vhost: add NULL pointer checking

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi,

On 03/21/2018 04:03 AM, zhiyong.yang@intel.com wrote:
> When vhost user PMD works in client mode to connect/reconnect virtio-user
> with server mode, new thread sometimes may run to new_device before
> queue_setup has been done, So have to wait until memory allocation is
> done.
> 
> Release note is updated in the patch.
> 
> Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> ---
>   doc/guides/rel_notes/release_18_05.rst | 7 +++++++
>   drivers/net/vhost/rte_eth_vhost.c      | 9 +++++++++
>   2 files changed, 16 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/release_18_05.rst b/doc/guides/rel_notes/release_18_05.rst
> index 3923dc253..7b301f021 100644
> --- a/doc/guides/rel_notes/release_18_05.rst
> +++ b/doc/guides/rel_notes/release_18_05.rst
> @@ -41,6 +41,13 @@ New Features
>        Also, make sure to start the actual text at the margin.
>        =========================================================
>   
> +* **Added support for virtio-user server mode.**
> +
> +  In a container environment if the vhost-user backend restarts, there's no way
> +  for it to reconnect to virtio-user. To address this, support for server mode
> +  is added. In this mode the socket file is created by virtio-user, which the
> +  backend then connects to. This means that if the backend restarts, it can
> +  reconnect to virtio-user and continue communications.

I think this shouldn't be part of this patch.

>   
>   API Changes
>   -----------
> diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
> index 3aae01c39..2490bad0b 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -580,6 +580,15 @@ new_device(int vid)
>   		eth_dev->data->numa_node = newnode;
>   #endif
>   
> +	/* The thread may run here before eth_dev->data->rx_queues or
> +	 * eth_dev->data->tx_queues have gotten valid memory, so have to
> +	 * wait until memory allocation is done.
> +	 */
> +	while (!eth_dev->data->rx_queues ||
> +	       !eth_dev->data->tx_queues) {
> +		usleep(1);
> +	}
> +
>   	for (i = 0; i < eth_dev->data->nb_rx_queues; i++) {
>   		vq = eth_dev->data->rx_queues[i];
>   		if (vq == NULL)
> 

I don't like the idea of polling here.
It looks like Junjie is addressing the problem in a different way [0],
do you confirm it would work in your case?

Thanks,
Maxime

[0]: http://dpdk.org/dev/patchwork/patch/36643/